the ability to follow a microservices-based approach, where some components are built with .NET and others with Java, but all can run on a common, supported platform in Red Hat Enterprise Linux and OpenShift Container Platform.

the capacity to more easily develop new .NET Core workloads on Microsoft Windows. Customers can deploy and run on either Red Hat Enterprise Linux or Windows Server.

a heterogeneous data center, where the underlying infrastructure is capable of running .NET applications without having to rely solely on Windows Server.

1.2. Install .NET Core

Install .NET Core 2.0 and all of its dependencies.

$ sudo yum install rh-dotnet20 -y

Enable the rh-dotnet20 Software Collection environment so you can run dotnet commands in the bash shell.

Note

This procedure installs the .NET Core 2.0 SDK. A .NET Core 2.1 SDK is also available, which you can install via sudo yum install rh-dotnet20-dotnet-sdk-2.1. It can be installed and used side-by-side with the 2.0 SDK. By default, the 2.1 SDK takes precedence if you install both. You can use a global.json to explicitly select one or the other.

$ scl enable rh-dotnet20 bash

Note

This command does not persist; it creates a new shell, and the dotnet command is only available within that shell. If you log out, use another shell, or open up a new terminal, the dotnet command is no longer enabled.

Warning

Red Hat does not recommend permanently enabling rh-dotnet20 because it may affect other programs. For example, rh-dotnet20 includes a version of libcurl that differs from the base RHEL version. This may lead to issues in programs that do not expect a different verison of libcurl. If you want to permanently enable rh-dotnet for yourself, add the following line to your ~/.bashrc file.

1.4. Publish Applications

The .NET Core 2.0 applications can be published to use a shared system-wide version of .NET Core or to include .NET Core. These two deployment types are called framework-dependent deployment (FDD) and self-contained deployment (SCD), respectively.

For RHEL, we recommend publishing by FDD. This method ensures the application is using an up-to-date version of .NET Core, built by Red Hat, that includes a specific set of native dependencies. These native libraries are part of the dotnet Software Collection. On the other hand, SCD uses a runtime built by Microsoft and uses the global Red Hat Enterprise Linux libraries. There are known issues when using .NET Core with these libraries.

1.4.1. Publish .NET Core Applications

Use the following command to publish an application using the FDD.

$ dotnet publish -f netcoreapp2.0 -c Release

If the application will only be used on RHEL, you can trim the dependencies needed for other platforms by using these commands.

1.4.2. Publish ASP.NET Core Applications

By default, ASP.NET Core 2.0 web applications are published with a dependency on a runtime store. This is a set of packages that are expected to be available on the runtime system. They are not included with the published application. RHEL does not include the ASP.NET runtime store, so the applications must be published, including all dependencies. This can be done by setting the PublishWithAspNetCoreTargetManifest property to false in the project file.

1.5. Run Applications on Docker

This section shows how to use the dotnet/dotnet-20-runtime-rhel7 image to run your application inside a Docker container. It requires you to have the docker binary installed, the docker daemon running, and the rh-dotnet20 Software Collection enabled.

Chapter 2. .NET Core 2.0 on Red Hat OpenShift Container Platform

2.1. Install Image Streams

The .NET Core image streams definition can be defined globally in the openshift namespace or locally in your specific project.

If you are a system administrator or otherwise have sufficient permissions, change to the openshift project. Using the openshift project allows you to globally update the image stream definitions.

$ oc project openshift

If you do not have permissions to use the openshift project, you can still update your project definitions starting with Step 2.

Run the following command to list all available .NET Core image versions.

$ oc describe is dotnet

The output shows installed images or the message Error from server (NotFound) if no images are installed.

To pull the images, OpenShift needs credentials for authenticating with the registry.redhat.io server. These credentials are stored in a secret.

Note

For OpenShift 3.11 and later, a secret is preconfigured for the openshift namespace.

Enter the following command to list secrets. The first column shows the secret name.

$ oc get secret | grep kubernetes.io/dockercfg

To check the contents of a secret, you can decode the .dockercfg or .dockercfgjson data from Base64 format. This allows you to see if you already have credentials for the registry.redhat.io server. Enter the following command to show the .dockercfg section in a secret.

You need to add a secret if there is no secret listed with credentials for the registry.redhat.io server.

Red Hat account credentials are used for registry.redhat.io access. If you are a customer with entitlements to Red Hat products, you already have account credentials to use. These are typically the same credentials used to log in to the Red Hat Customer Portal. To verify your Red Hat credentials, enter the following command and attempt to log in.

$ docker login registry.redhat.io

If you cannot log in, you first need to get an account with Red Hat. See Red Hat Container Registry Authentication for additional information. If you can log in, enter the following commands to create the secret.

As suggested by the output of the new-app command, you can track progress of the build using the oc logs command.

$ oc logs -f bc/exampleapp

Once the build is finished, you can see the deployed application.

$ oc logs -f dc/exampleapp

At this point, the application is accessible within the project. To make it accessible externally, use the oc expose command. You can then use oc get routes to find the URL.

$ oc expose svc/exampleapp
$ oc get routes

2.3. Environment Variables

The .NET Core images support a number of environment variables to control the build behavior of your .NET Core application. These variables can be set as part of the build configuration, or they can be added to an .s2i/environment file in the application source code repository.

Variable Name

Description

Default

DOTNET_STARTUP_PROJECT

Used to select the project to run. This must be a project file (for example, csproj or fsproj) or a folder containing a single project file.

.

DOTNET_SDK_VERSION

Used to select the default sdk version when building. If there is a global.json file in the source repository, that takes precedence. When set to latest the latest sdk in the image is used.

Lowest sdk version available in the image

DOTNET_ASSEMBLY_NAME

Used to select the assembly to run. This must not include the .dll extension. Set this to the output assembly name specified in csproj (PropertyGroup/AssemblyName).

Name of the csproj file

DOTNET_RESTORE_SOURCES

Used to specify the space-separated list of NuGet package sources used during the restore operation. This overrides all of the sources specified in the NuGet.config file.

DOTNET_NPM_TOOLS

Used to specify a list of NPM packages to install before building the application.

DOTNET_TEST_PROJECTS

Used to specify the list of test projects to test. This must be project files or folders containing a single project file. dotnet test is invoked for each item.

DOTNET_VERBOSITY

Used to specify the verbosity of the dotnet build commands. When set, the environment variables are printed at the start of the build. This variable can be set to one of the msbuild verbosity values (q[uiet], m[inimal], n[ormal], d[etailed], and diag[nostic]).

DOTNET_CONFIGURATION

Used to run the application in Debug or Release mode. This value should be either Release or Debug.

Release

ASPNETCORE_URLS

This variable is set to http://*:8080 to configure ASP.NET Core to use the port exposed by the image. Changing this is not recommended.

2.4. Sample Applications

dotnet-example: This is the default model–view–controller (MVC) application.

dotnet-runtime-example: This shows how to build an MVC application using a chained build and the .NET runtime image.

dotnet-pgsql-persistent: This is the Microsoft ASP.NET Core MusicStore sample application using a PostgreSQL backend.

To add the samples using the OpenShift Web Console, browse to your project and click Add to project. You can filter for dotnet. If the samples do not show up, you can add them to your installation by running the following commands.

2.5. Create a Runtime Image

The .NET Core runtime image contains the files sufficient to run a .NET application, but not to build one. As such, you must provide an already published application for the runtime image. This can be a static application inside of an image that layers on top of the runtime image or a new image can be built that is fed the application from a build image. This last method is commonly referred to as chaining builds.

Deploying a build chain requires a more in-depth configuration than a simple application build. At a minimum, a build chain needs:

In this template, we define a *-build and a *-runtime build config. The build image builds from a GitHub project and has a trigger to rebuild automatically when the project changes or when the base image (in this case, dotnet-20-rhel7) updates.

The runtime image builds from the dotnet-20-runtime-rhel7 base image but pulls a tar.gz file from the build image that contains the build project. That is done using this source definition in the build config.

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